His mom wrote a letter to the Make-A-Wish Foundation–a national children's charity that grants wishes of kids with life-threatening medical conditions–explaining how her son's dream is to work on Wall Street.

Now that he's finished with chemotherapy that dream is coming true.

Make-A-Wish teamed up with Goldman Sachs and to give Grinner a week-long investment banking internship in New York City.

"It's meant so much to me. It's something that I've always dreamed of," Grinner told Business Insider in a telephone interview. "I used to work a 40-hour work week to support my family back home. The fact they are giving me this opportunity is truly amazing."

The bank and various other Make-A-Wish partners have pulled out all the stops to give him the ultimate Wall Street experience. Grinner's itinerary includes ringing the opening bell at the Nasdaq with BlackRock, touring Yankees Stadium and meeting Derek Jeter, visiting the New York Stock Exchange and meeting floor brokers, making an appearance on CNBC's "Power Lunch" and meeting with Goldman CEO Lloyd Blankfein and the firm's other top executives.

Photo courtesy of Make-A-Wish

As part of his internship, he also received made-to-order suits from Ralph Lauren and a pair of designer shoes.

Grinner graduated from high school this June. His favorite subjects include economics and history. He loves things that are complex and said this is what attracted him to finance.

"I have a deep interest in complicated things," Grinner told us. "So far, investing has been the most complicated thing I have ever attempted to understand – bonds, futures, IPOs, mergers & acquisitions–and the way they connect to global markets and global news is amazing to me."

During his junior year, his economics teacher gave the class a project to actively trade the stock market using $50,000 in imaginary capital.

"I became obsessed with it. I started practicing different forms of analysis to perfect what I was doing."

After three months, Grinner's portfolio was up to $75,000 while most of his classmates had zeroed out their accounts.

Now he's getting a glimpse into what life's like on the Street.

When he arrived at Goldman's headquarters, he was introduced over the trading floor's PA system. He received a standing ovation from all of the traders. He said the people at the firm have been incredible.

Photo courtesy of Make-A-Wish

"The people are a lot nicer than they're put out to be in the media," he said. "They're absolutely incredible. They're willing to show me the intricate parts of this business and explain to me how this works."

Goldman managing director John Underwood, who is on the advisory council for Make-A-Wish in San Francisco, said folks at the firm have gone above and beyond.

"The whole point of this was to really give Tre a feel of what it's like to be an investment banker–that's a big word that cover all the different areas," Underwood told us. "The response has been overwhelming. I've had partners who were so impressed with this young man. They've asked if they could follow up...It's gone well beyond my own expectations."

Grinner hopes to one day return to Wall Street for his career. Right now, he's leaning toward going into Fixed Income.